It is the purpose of this study to examine the pathophysiology of hypertension associated with renal disease. Sequential hemodynamic changes of intra-arterial blood pressure, cardiac output and peripheral vascular resistance in patients with end-stage renal disease will be determined both before and after bilateral nephrectomy under the following conditions: (1). Salt loading and depletion (2). Chronic expansion and contraction of the blood volume. The serial hemodynamic changes will be correlated with changes in peripheral plasma renin activity and circulatory catecholamines. These studies should enable us to define the relationship among intra-vascular volume, total exchangeable sodium, the renin-angiotensin system and the sympathetic nervous system in the pathogenesis of hypertension of renal origin.